Cochlear implants have restored hearing to approximately 100,000 severely to profoundly deaf people worldwide. Most implant users are able to understand speech in quiet without lip-reading, and many can use the telephone. However there are still challenges for the cochlear implant user, including speech recognition in noise, music perception, identifying tone of voice and discriminating different people's voices. These tasks rely on good voice pitch or musical pitch perception. Current speech processing algorithms provide only very coarse pitch information; they present just the amplitude envelope of the signal and discard the fine structure. In an effort to improve hearing, some people now choose to receive a second cochlear implant in the other ear - bilateral implants. This provides some benefit, but it still does not solve problems in many everyday listening situations. There are also disadvantages of increased cost, risk and loss of residual hearing. Furthermore damage to both inner ears resulting from the implants may endanger benefit from future technologies like hair cell regeneration. One method to provide pitch information is to add acoustic hearing to the non-implanted ear with a hearing aid. This is called bimodal hearing. This project examines the performance of bilateral cochlear implant users on four tasks relying on pitch perception, using a comparison group of bimodal users. The specific aims are to compare the mean group scores of eight experienced bilateral and bimodal adult users on: 1) sentence recognition with a competing female talker using Hearing in Noise Test spoken by a male; 2) music perception using the Montreal Battery of Evaluation of Amusia; 3) intonation discrimination using the Aprosodia battery; and 4) talker identification using vowels spoken by ten different talkers. Results from this study will assist in the counseling of patients who are facing an important clinical decision: whether to receive a second cochlear implant or continue with one implant plus a hearing aid. Relevance: Bilateral cochlear implantation is expensive, usually involves two surgeries and risks the loss of residual hearing. It may not be the best option for all implant users. More information on the relative benefits of bilateral and bimodal stimulation is required to aid thousands of patients and parents considering a second cochlear implant surgery. [unreadable] [unreadable] [unreadable]